Cyclonic vacuum cleaners are known in the art. In addition, cyclonic vacuum cleaners which comprise a first stage cyclone and plurality of second stage cyclones are known. An example is shown in Conrad (U.S. Pat. No. 6,782,585). As shown therein, a vacuum cleaner has a first cyclonic cleaning stage comprising a single first stage cyclone and a second cyclonic cleaning stage downstream from the first cyclonic cleaning stage and comprising a plurality of cyclones in parallel.
The plurality of second stage cyclones typically remove particulate matter finer than the particulate matter that is removed in the first cyclonic cleaning stage. Accordingly, the coarsest particulate matter that is entrained in an air stream is removed in the first cyclonic cleaning stage and finer particulate matter is removed in the downstream cyclonic cleaning stage. However, the air exiting the second cyclonic cleaning stage may still contain sufficient particulate matter to damage a suction motor positioned downstream from the second cyclonic cleaning stage. Accordingly, as shown in Conrad, a filter may be positioned downstream from the second cyclonic cleaning stage and upstream from the suction motor.